首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   213篇
  免费   13篇
林业   13篇
农学   11篇
基础科学   1篇
  58篇
综合类   8篇
农作物   52篇
水产渔业   25篇
畜牧兽医   43篇
园艺   4篇
植物保护   11篇
  2022年   12篇
  2021年   15篇
  2020年   13篇
  2019年   11篇
  2018年   16篇
  2017年   22篇
  2016年   22篇
  2015年   7篇
  2014年   10篇
  2013年   27篇
  2012年   14篇
  2011年   17篇
  2010年   5篇
  2009年   6篇
  2008年   16篇
  2007年   2篇
  2006年   3篇
  2005年   3篇
  2004年   1篇
  2000年   1篇
  1985年   1篇
  1983年   2篇
排序方式: 共有226条查询结果,搜索用时 15 毫秒
141.
Melanoma is one of the most aggressive cancers of all solid tumors. The effect of angiotensin II on expression of three Matrix Metalloproteinases (MMPs) and Vascular Endothelial Growth Factor (VEGF) in B16F10 melanoma cells was evaluated. Also the blocking effect of losartan on angiotensin II induced effects was assessed. B16F10 murine melanoma cells were cultured in RPMI-1640 medium supplemented with 10% Fetal Bovine Serum (FBS) and 24 h prior to experiment the serum free medium was used. Angiotensin II (0 M, 10(-10) M, 10(-9) M or 10(-8) M) alone or in combination with Losartan (10(-6) M) in RPMI-1640 replaced the medium for experiments. After the incubation time (0, 1, 2, 6 and 12 h) cells were harvested using 0.05% (w/v) Trypsin and then recovered by centrifugation. The expression of MMP-2, MMP-13, MMP-9 and VEGF in B16F10 cell lysate was assessed by immunoblotting. Angiotensin II significantly enhanced the expression of MMP-2, MMP-13 and VEGF by concentrations as low as 0.1 nM. But angiotensin II could not stimulate any significant increase in MMP-9 expression by angiotensin II in B16F10 cells. Losartan abolished the enhancing effect of every concentration of angiotensin II on MMP-2, MMP-13 and VEGF expression completely and in all incubation times. As a result, angiotensin II through activation of AT1 receptors can stimulate the expression of MMP-2, MMP-13 and VEGF in B16F10 melanoma cells. This is an important conclusion because of the importance of these factors in melanoma invasiveness and the possible important role that angiotensin receptor blockers may play as cancer medications.  相似文献   
142.

Background:

Apolipoprotein A2 (APOA2) is the second major apolipoprotein of the high-density lipoprotein cholesterol (HDL-C). The study aim was to identify APOA2 gene variation in individuals within two extreme tails of HDL-C levels and its relationship with HDL-C level.

Methods:

This cross-sectional survey was conducted on participants from Tehran Glucose and Lipid Study (TLGS) at Research Institute for Endocrine Sciences, Tehran, Iran from April 2012 to February 2013. In total, 79 individuals with extreme low HDL-C levels (≤5th percentile for age and gender) and 63 individuals with extreme high HDL-C levels (≥95th percentile for age and gender) were selected. Variants were identified using DNA amplification and direct sequencing.

Results:

Screen of all exons and the core promoter region of APOA2 gene identified nine single nucleotide substitutions and one microsatellite; five of which were known and four were new variants. Of these nine variants, two were common tag single nucleotide polymorphisms (SNPs) and seven were rare SNPs. Both exonic substitutions were missense mutations and caused an amino acid change. There was a significant association between the new missense mutation (variant Chr.1:16119226, Ala98Pro) and HDL-C level.

Conclusion:

None of two common tag SNPs of rs6413453 and rs5082 contributes to the HDL-C trait in Iranian population, but a new missense mutation in APOA2 in our population has a significant association with HDL-C.  相似文献   
143.
Background: During antigen capture and processing, mature dendritic cells (DC) express large amounts of peptide-MHC complexes and accessory molecules on their surface. DC are antigen-presenting cells that have an important role in tolerance and autoimmunity. The transforming growth factor-beta1 (TGF-Beta1) cytokine has a regulatory role on the immune and non-immune cells. The aim of this study is to evaluate the effect of TGF-Beta1 on the induction of human leukocyte antigen-G (HLA-G) expression on the DC which is derived from monocyte. Methods: In this study, we evaluated the effect of TGF-Beta1 in induction HLA-G expression on the monocyte-derived DC by flowcytometry and then CD4+ T cell proliferative responses in the presence of DC-treated TGF-Beta1 was studied. Results: The results of this study showed that DC bearing HLA-G down-regulated activation of CD4+ T cells and production of IL-6 and IL-17 in comparison with control (P<0.05). Conclusion: It is concluded that TGF-Beta1 has an important regulatory role in CD4+ T cell proliferation by increasing HLA-G on DC and these cells can probably prevent unexpected immune responses in vivo.  相似文献   
144.
145.
146.
Mathematical models employing textural data are commonly used for the estimation of the particle-size distribution (PSD) curve. In this study, two models were used: (1) the model proposed by Fredlund et al. (2000) (F model), and (2) the model proposed by Skaggs et al. (2001) later modified by Fooladmand and Sepaskhah (2006) (FS model). Comparison of the results obtained by these two models, applied for 30 soils from the south of Iran, showed that the F model was better when the model parameters were determined by setting minimum differences between the measured and estimated PSD curve. Also, three equations based on soil textural data were derived for estimating parameters of the F model, and these equations were used to estimate the PSD curve. The results showed that for 10 independent soils from the south of Iran and 50 soils from the UNSODA database, the FS model was better than the F model based on three new derived equations. Therefore, the FS model can be safely used to estimate the PSD curve with different soil textures; however, the F model is appropriate for representation of the measured PSD curve.  相似文献   
147.
In this study, the effects of penconazole (PEN) and calcium (Ca) on growth amelioration and quality of seed oil in canola (Brassica napus L.) under drought stress were investigated. Drought stress reduced the growth parameters (fresh weight and dry weight) in canola; however the application of PEN and Ca improved these parameters under drought condition. Inducing effect of Ca on protein content was more prominent than PEN. Proline content increased under drought stress and PEN and Ca treatment caused more induction it under drought. PEN and Ca alleviated the negative effects of drought stress in canola by inducing antioxidant defense. The application of PEN and Ca caused a significant reduction in lipid peroxidation and hydrogen peroxide and mitigation of the drought induced oxidative stress. Drought stress induced protein content, total phenol, flavonol content, soluble sugar, palmitic acid and palmitoloic acid, and reduced flavonoid content, oleic acid, linolenic acid, and linolonoic acid in canola seed. PEN and Ca increased palmitic acid, linoleic acid (Omega-6), linolenic acid (Omega-3), oleic acid, protein, and soluble sugar. Our results indicated that application of PEN and Ca enables canola plants to withstand the deleterious impact of drought stress and caused improvement of antioxidant capacity, essential fatty acids (linolenic acid and linolonoic acid) and oil quality in canola seed.  相似文献   
148.
A novel dye degrading bacterium capable of decolorizing and mineralizing four different dyes (Methyl red, Orange II, Direct red 80, and Direct blue 71) was isolated from textile industrial wastewater using the selective enrichment technique. The bacterium was identified as Pseudomonas aeruginosa. More than 80 % decolorization of Direct red 80 was obtained under microaerophilic conditions in 48 h, whereas only 10 % color removal was obtained under oxic conditions at the same time. Subsequent aeration of the decolorized medium resulted in the mineralization of the metabolic intermediates generated after azo bond cleavage by P. aeruginosa as confirmed by total organic carbon content and high-performance liquid chromatography analyses. The degradation products were characterized by Fourier transform infrared spectrometer and nuclear magnetic resonance techniques whereas the biotoxicity profile of the samples were evaluated using the brine shrimp lethality test assay. Data from this study provide evidence of dye mineralization and detoxification by a monoculture of P. aeruginosa in successive microaerophilic/oxic stages.  相似文献   
149.
Abstract

The aim of this study was to investigate the influence of different compositions of nitrogen (N) sources on yield and nutritional quality in potato cultivars (Solanum tuberosum L.). The experiment used a factorial arrangement as two factors in randomized complete block design. Factor (A) was nitrogen sources: control, 75% M?+?25%V, 50% M?+?50%V, 100% M, where M plots received nitrogen from mineral fertilizer and V plots received nitrogen from vermicompost. Factor (B) was potato cultivars (Sante and Savalan). In Sante cultivar, 75% M?+?25%V produced the highest total and marketable yield. In Savalan, cultivar application of vermicompost in 75% M?+?25%V and 50% M?+?50%V increased significantly total and marketable yield as compared with 100% M. Application of vermicompost significantly decreases tuber nitrate content and increases nitrogen-use efficiency. In Savalan, cultivar 50% V?+?50%M and in Sante cultivar 75% V?+?25%M can effectively be used for improving yield and nutritional quality of tuber.  相似文献   
150.
1. In poultry investigations, the main interest is often to study the effects of many factors simultaneously. Two or three level factorial designs are the most commonly used for this type of investigation. However, it is often too costly to perform when number of factors increase. So a fractional factorial design, which is a subset or a fraction of a full factorial design, is an alternative. The Taguchi method has been proposed for simplifying and standardising fractional factorial designs.

2. An experiment was conducted to evaluate the applicability of the Taguchi method to optimise in vitro intrinsic phytase activity (IPA) of rye, wheat and barley under different culture conditions.

3. In order to have a solid base for judging the suitability of the Taguchi method, the results of the Taguchi method were compared with those of an experiment that was conducted as a 34 full factorial arrangement with three feed ingredients (rye, wheat and barley), three temperatures (20°C, 38°C and 55°C), three pH values (3.0, 5.5 and 8.0) and three incubation times (30, 60 and 120 min), with two replicates per treatment.

4. After data collection, a Taguchi L 9 (34) orthogonal array was used to estimate the effects of different factors on the IPA, based on a subset of only 9 instead of 81 treatments. The data were analysed with both Taguchi and full factorial methods and the main effects and the optimal combinations of these 4 factors were obtained for each method.

5. The results indicated that according to both the full factorial experimental design and the Taguchi method, the optimal culture conditions were obtained with the following combination: rye, pH = 3, temperature = 20 °C and time of incubation = 30 min. The comparison between the Taguchi and full factorial results showed that the Taguchi method is a sufficient and resource saving alternative to the full factorial design in poultry science.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号